Aims and background: In the last decades, many epidemiological studies have implicated outdoor environmental carcinogens in the onset of lung cancer. The present investigation evaluated lung cancer mortality in two areas of the Province of La Spezia (Northern Italy) exposed to environmental pollution emitted by a coal-fired power station and other industrial sources, including a waste incinerator.
Methods: In the two exposed areas, lung cancer mortality risk for the 1988-1996 calendar period was evaluated using the whole Province population as referent. The corresponding relative risks (RR) were estimated after controlling for age structure, urban/rural gradient and deprivation factors (occupation, education, home ownership, housing conditions and family structure) by a Poisson regression modeling. The geographic pattern of risk for the whole province was evaluated via the Besag, York and Mollié (BYM) bayesian model.
Results: Persons living in urban areas showed the highest rates in both sexes. No statistically significant risk excess was found in the two exposed areas among males, after excluding rural and semi-rural zones from the analyses (RR = 1.03 and RR = 0.77). In contrast, a risk excess was observed for females in both exposed areas, which remained elevated and statistically significant (P <0.05) after restriction to urban/semi-urban municipalities and after controlling for deprivation factors (RR = 1.54 and RR = 2.14, respectively). Bayesian mapping confirmed the rural/urban gradient and the risk excess observed in females near the industrial sites.
Conclusions: The risk observed among females is consistent with pollution measurements and with other epidemiologic findings, whereas a strong confounding from occupational exposures and smoking habit could account for the lack of an excess risk in males. However, the ecologic nature of this investigation prevented drawing a causal inference. The pollution-related risk observed in the female gender is an important clue that deserves further epidemiologic attention.